Frequently Asked Questions

  • Arsenic is a toxic element. It occurs naturally in rocks and soils, and can occur in groundwater.                                                                                                                                         
  • The main toxic form of arsenic is inorganic arsenic. Water arsenic compounds are inorganic and toxic.                                                                                                                           
  • There are also organic forms of arsenic in seafood. Seafood arsenic compounds are not toxic.

Arsenic in New Jersey well water is almost always naturally occurring.  It dissolves into groundwater from arsenic-bearing minerals in many of the bedrock aquifers of Northern and Central New Jersey.

  • Naturally occurring arsenic in groundwater used for drinking is a major source of inorganic arsenic exposure. Groundwater contamination occurs when, under certain conditions, naturally occurring arsenic deposits in bedrock dissolve and seep into groundwater.
  • The main exposure to arsenic is via ingestion of drinking and cooking water, because arsenic is poorly absorbed through the skin.  However, treating all the water in the home is the most effective way to reduce arsenic exposure. 
  • During gestation, the developing fetus is exposed to arsenic via passage across the placenta from mother's blood to the baby's blood. In contrast, breast milk is safe, and does not contain inorganic arsenic.
  • The information provided here is focused on groundwater from private wells since it can be a common route of exposure for people; however, some exposure can also come from low levels of arsenic in certain foods. More information on exposure from food and other sources besides groundwater is available at
  • Arsenic is a well-established carcinogen, causing liver, bladder, kidney, lung and skin cancer.
  • Other associated health effects include heart disease, diabetes, immune effects and respiratory problems.
  • In children, exposure is also associated with defects in intelligence
  • Arsenic crosses the placenta and may affect fetal development.
  • Infants and children may be more sensitive to the effects of arsenic than adults.
  • In utero and early life arsenic exposure has been linked to adverse effects later in life, including increased risks of respiratory disease, cardiovascular disease and certain cancers as adults.
  • The most immediate option is to switch to bottled water for all drinking and cooking. Note that simple water filters (such as the activated carbon filters) available in the hardware store are NOT effective for arsenic removal. Note also that boiling water DOES NOT remove arsenic from water.
  • If your water has elevated arsenic, information on treatment options and providers is available at and
  • Long term, families should strongly consider either installing an appropriate treatment system or connecting to a public water supply if possible. If a treatment system is installed, water should be tested annually to ensure water is safe for arsenic and the system is working. The State of NJ has a 0% interest 10-year loan program to help homeowners spread the initial cost of buying and installing the units. 
  • We do not recommend testing for urine or blood arsenic levels at this time. Several types of tests are available; however, results can be difficult to interpret because there are no widely accepted standard values to distinguish "normal" from "elevated" test results. Test results can also be misleading if seafood was consumed during the week prior to arsenic testing, as the forms of arsenic derived from seafood are not toxic and complicate the interpretation of internal arsenic levels.
  • Instead, you are encouraged to take action to ensure that you are using a safe water source for drinking and cooking. Once arsenic in the source is reduced, blood levels of arsenic will also rapidly decline. 
  • Arsenic has no smell, taste or color when dissolved in water, even in high concentrations.
  • Testing a water sample is the only way to know how much arsenic is present in a well.
  • EPA regulations and testing are limited to public water sources, not private wells. If your family gets their drinking/cooking water from a private well, you should have your water tested for arsenic. 
  • It is not recommended that homeowners go out and buy a home test kit to check arsenic levels in their water.
  • NJDEP's Office of Quality Assurance provides lists of certified labs and they can be reached by phone at 609-292-3950 for more information.
  • The labs listed on the NJ Arsenic Awareness Testing Options page are certified to sample private wells and analyze drinking water for arsenic by the most sensitive method available (EPA 200.8). Clicking on the laboratory name will bring you to their website
  • Raritan Headwaters Association offers discounted water tests for a wide variety of pollutants to individual watershed residents and also partners with participating municipalities on designated test days. 908-234-1852, x401


  • If your well water has not been tested within the past 5 years county health officers recommend requesting testing for the full set of Private Well Testing Act contaminants
  • If your well water has ever exceeded state standards for any of the contaminants it should be tested yearly for those contaminants, including where treatment systems have been installed.
  • Residents of every county where arsenic may be an issue (Bergen, Essex, Hudson, Hunterdon, Mercer, Middlesex, Morrris, Passaic, Somerset, Sussex, Union, and Warren) should also test for total coliform, e. coli if positive for total coliform, nitrate, iron, manganese, pH, VOCs, lead and gross alpha in addition to arsenic. 
  • Yearly tests for total coliform, e. coli if positive for total coliform, and nitrates are recommended. 
  • In New Jersey, the standard for arsenic is 5 micrograms per liter (abbreviated as "μg/L"). If arsenic levels are greater than 5 micrograms/liter, we encourage the use of bottled and/or properly treated water for all drinking and cooking, and encourage the installation of a treatment system.
  • Importantly, a negative test for arsenic does not mean that your water is safe with respect to other water quality parameters.
  • The MCL is an enforceable standard for public water systems regulated under the Safe Drinking Water Act. Private wells are unregulated and owners are responsible for managing the safety of their own drinking water; therefore, this standard only serves as a guideline value. Private well users must decide for themselves what concentration of arsenic in their drinking water is acceptable.
  • The Federal MCL for arsenic is 10 μg/L, chosen in 2001 by the Environmental Protection Agency (EPA) using discretionary authority to consider the costs of treating publicly supplied water to meet this standard. The State of New Jersey has adopted a lower MCL of 5 μg/L, the most protective in the nation. However, arsenic is a known carcinogen; therefore the EPA also set an MCL-Goal for arsenic of 0 μg/L, meaning there is no level of arsenic in drinking water that can be considered safe.
  • The risks from drinking water with arsenic at the federal MCL of 10 μg/L are significantly higher than for other carcinogenic drinking water contaminants at their MCL.
  • The maximum contaminant level goal (MCLG) is defined by USEPA as the level of contaminant in drinking water below which there is no known or expected risk to health and which allows a margin of safety. Because arsenic is a known human carcinogen via drinking water, the USEPA has determined that the maximum contaminant level goal is zero for arsenic in drinking water.
  • The MCLG is usually lower than the Maximum Contaminant Level (MCL). The MCL is the highest level of a contaminant that is legally allowed in drinking water.  MCLs are set as close as feasible to the MCLGs. For arsenic, the New Jersey MCL is 5 mcg/l. 
  • In New Jersey well water there are two common forms of arsenic that need to be removed by water treatment, Arsenic 3 and Arsenic 5.
  • Arsenic 3 is much more difficult to remove from well water than Arsenic 5 because Arsenic 3 has a neutral charge.
    • There is no simple and affordable test commercially available to determine which arsenic species is present so the species of arsenic present is usually unknown, though there is a rule of thumb that can help (See FAQ below).
  • The New Jersey Geological and Water Survey estimates that 20% of New Jersey wells with arsenic above the Maximum Contaminant Limit (MCL) of 5 micrograms/liter (mcg/L) have significant concentrations of Arsenic 3. 
  • There is no simple and affordable test commercially available to determine which arsenic species is present so the species of arsenic present is usually unknown. 
  • There is an Arsenic Speciation "Rule of Thumb" developed by the New Jersey Geological and Water Survey and Rutgers University that can be used to determine if Arsenic 3 may be a factor or not.
  • The Arsenic Speciation Rule of Thumb works by answering these two questions:
    • Are the Iron or Manganese concentrations in the untreated well water greater than 50 micrograms/liter (mcg/L)?
    • Is the Dissolved Oxygen concentration in the untreated well water less than 1.0 milligrams/liter (mg/L)?
  • If the answer to each question is "no" it is very unlikely that the water contains a significant concentration of Arsenic 3. 
  • If the answer to either question is "yes" then Arsenic 3 is likely present at a concentration greater than 3 mcg/L and therefore a serious factor in water treatment selection. In this case, a confirmatory Arsenic 3 test by arsenic speciation cartridge or laboratory analysis is recommended before spending extra money on treatment components to convert Arsenic 3 to Arsenic 5.
  • The Act requires that, when property with certain types of drinking water wells is sold or leased, the well water must be tested for contaminants. The results of the water testing must be reviewed by both the buyer and the seller, or in the case of a leased property, by the lessee.
  • The Act covers SALES of two types of properties and LEASES of other properties. Testing is required for the following:
    • SALE of any property that gets its drinking water from a private well located on the property, and
    • SALE of any property that gets its drinking water from a well that has less than 15 service connections or that does not regularly serve an average of at lweast 25 peole daily at least 60 days out of each year.
    • Leasing of any property that gets its drinking water from a private well that isn't required to be tested under any other State law.
  • In the case of a home sale, the buyer of the home should always choose the type of water treatment system and who will install it. This is important so the person living with the system will know what they have, how to monitor and maintain it, and who to call for service, because of course the buyer is the one who will be drinking the water.
  • Every contract of sale for a property subject to the Act must include a provision requiring the testing as a condition of the sale.
  • A closing of the title of sale on a real property that is subject to the Act may not occur unless both the buyer and seller have received and reviewed a copy of the water test results, and have signed a paper certifying that they have received and reviewed a copy of the results.
  • Every time a rental property subject to the Act is leased, a written copy of the most recent test results must be given to the lessee.
  • That depends on where you live.
  • All wells must be tested for the following contaminants: total coliform bacteria, iron, manganese, pH, all volatile organic compounds (VOCs) with established Maximum Contaminat Levels, nitrate and lead. If total coliform bacteria are detected, a test must also be conducted for fecal coliform or E. coli.
  • Private wells in certain counties will also have to test for arsenic, mercury, and 48-hour rapid gross alpha particle activity. 
  • Arsenic tests are required in Bergen, Essex, Hudson, Hunterdon, Mercer, Middlesex, Morris, Passaic, Somerset, Sussex, Union and Warren counties. 
  • Click here for a table showing all the contaminants that must be tested.
  • Surveyed treatment providers in New Jersey and the New Jersey Department of Environmental Protection recommend adsorption systems to treat arsenic in private wells.  The biggest decision buyers are faced with is whether to treat all the water in the house or a single tap in the kitchen.
  • The preferred system is a Whole-House treatment system with two tanks in series, which is often called "Point-of-Entry" (POE) because it treats all water in the home near the point where the water enters the home.
  • The other type of treatment is single tap treatment, which is often called "Point-of-Use" (POU) because the treatment unit is usually near the single tap used for drinking and cooking water.
  • The recommended arsenic treatment system is a Whole House two-tank adsorption system with the following components:
  1. Two Whole-House arsenic treatment tanks in series with a high capacity arsenic treatment media
  2. A sampling port between the two arsenic tanks
  3. A 5 micron sediment pre-filter before the arsenic tanks (depending on whether other water treatment elements are in place before the arsenic tanks)
  4. A 5 micron sediment post-filter after the arsenic tanks
  5. A water meter
An effective system also needs to be maintained. To qualify as a well maintained system, a water test must be conducted yearly from the kitchen sink and the sampling port between the two arsenic tanks.  If the arsenic between the tanks is greater than 5 mcg/l, your water treatment professional should remove the worker tank, replace it with the safety tank and install  a new safety tank.  

One-tank POE system disadvantages:

    • With no back-up/safety tank homeowners are at risk of drinking water with unhealthy levels of arsenic during the period after the arsenic begins to break through the treatment media and before the next testing.

One-tank POE system advantages:

    • Cheaper in the short term
  • A one-tank POE system is cheaper in the short term, but with no back-up/safety tank homeowners are at risk of drinking water with unhealthy levels of arsenic during the period after the arsenic begins to break through and before the next testing.
  • The water goes through the first tank and then through the second tank.  We call the first tank the "worker tank" because it does the most work removing arsenic. When the worker tank is new it will remove all the arsenic, but after about one year (depending on the arsenic level and how much water is used), the worker tank's arsenic removal efficiency will start to decline and some arsenic will start to break through the worker tank. When this occurs, the second tank will remove the arsenic, and this is why we call the second tank the "safety tank".
  • Without the safety tank you would be exposed to the arsenic getting through the worker tank.  With only a one-tank system you won't know you're being exposed to arsenic until the next water test is obtained.
  • A properly installed and maintained two-tank POE system will reduce your arsenic exposure to zero, which is the EPA maximum contaminant level goal for arsenic. A one-tank POE system can't meet this goal.
  • A two-tank POE system is also more economical over the life of the system. With one tank you'll need to change the tank as soon as the concentration gets near 5 mcg/l. Otherwise you will be exposed to arsenic levels above the state standard. However, with a two-tank POE system, you can safely conduct once per year sampling and not need to replace the worker tank until the concentration after the worker tank exceeds 5 mcg/l.  Even if the concentration after the worker tank goes up to 10 or 20 mcg/l, the safety tank will remove all of the arsenic before it reaches the taps in your home.
  • The typical two-tank POE arsenic water treatment system is 4-5 feet tall and requires a floor area of about 2 feet by 3 feet.
  • Most homeowners find space for these systems in their basement near the well water pressure tank.
  • It's important to realize that if you choose a less expensive arsenic treatment media it may have a lower capacity to absorb arsenic. This means you may need to replace the tanks more often and the system will likely cost you more over the long term.
  • DEP strongly recommends a 5-micron pre-treatment sediment filter to prevent any dirt or geologic materials coming up from the well from clogging or fouling the arsenic water treatment equipment. 
  • If a water softener or other treatment unit capable of removing dirt or other particles will be located before the arsenic water treatment unit, and the well water is not especially dirty, then the pre-treatment sediment filter can be considered optional.
  • A 5-micron size post-treatment sediment filter is essential to prevent any particles of treatment media, which may be highly enriched in arsenic, from getting into your drinking water supply. DEP staff have observed many cases of arsenic treatment media breakthrough.
  • Reverse Osmosis 
    • Reverse osmosis is not effective at removing Arsenic 3. There is no simple and affordable test commercially available to determine which arsenic species is present so the species of arsenic present is usually unknown, though there is a rule of thumb which can help (see FAQ above on "Testing your well").
    • Reverse osmosis can be an effective Point-of-Use (POU) treatment system for drinking and cooking water when Arsenic 3 is not present
    • POU reverse osmosis has been found to be a good backup in combination with a Whole-House POE arsenic removal system when only Arsenic 5 is present.
    • Whole-House reverse osmosis is not recommended due to cost, size of system, and the fact that reverse osmosis treated water should not be run through copper plumbing.
  • Anion Exchange Systems
    • Anion exchange systems are not effective at removing Arsenic 3. There is no simple and affordable test commercially available to determine which arsenic species is present so the species of arsenic present us usually unknown, though there is a rule of thumb which can help (see FAQ above on "Testing your well").
    • The anion exchange system requires regular maintenance that involves purchasing water softener salt to keep the brine tank filled. If the salt level is not maintained, the system will stop removing arsenic and will dump the previously removed arsenic into the home's water at a very elevated concentration.
    • When an anion exchange system runs through a regeneration cycle all of the arsenic captured by the system will be flushed out of the tank and discharged somewhere near the home, usually to the home's septic system.
    • For the above reasons, we strongly recommend against using anion exchange for arsenic removal even if only Arsenic 5 is present.
    • However, for well water with a high pH (pH>8.5), anion exchange can be an effective tool for lowering pH and can be used as pre-treatment in combination with a Whole-House Point-of-Entry (POE) arsenic removal system (see below on "Whole House vs. Point-of-Entry").
  • The following treatments are not effective for removing any arsenic:
    • Boiling water (this will increase the arsenic concentration)
    • Ultraviolet (UV) light
    • Cation exchange (commonly called a water softener)
    • Granular activated carbon (GAC)
    • Aeration
    • Magnetic water conditioners
    • Water filtration pitchers (Brita, etc.)
    • Water filtration from the refrigerator
    • Sediment filter


POE Advantages:

  • All water in the house is treated
  • Can drink water safely from any tap
  • Arsenic-free shower and bath water
  • Can easily size system to maintain flows the same as before the treatment system was installed


POE Disadvantages:

  • Installation cost
  • Maintenance cost (about $1 a day)
  • The POE system is the most protective of you and your family's health.
  • All water in the house is treated so any tap in the home can be used safely for drinking water.
  • Water for bathing, showering, brushing teeth, and laundry will also be arsenic-free.
  • A New Jersey study found that Whole-House arsenic water treatment provided more effective exposure reduction than Point-of-Use treatment. See this link for an abstract of the study.

  • The POE system has a higher initial cost but the New Jersey Housing and Mortgage Finance Agency offer no interest loans through its Potable Water Program to cover the cost of installation.
  • The POE system requires approximately 6 square feet of floor space in the basement, though it does not take up any space under the kitchen sink like a POU system would.

POU advantages:

  • When POU is used for a single tap, Installation cost is less for POU than for POE.
  • When POU is used for a single tap, maintenance cost is less for POU than for POE.

POU disadvantages:

  • Water from untreated taps still contains unhealthy levels of arsenic. 
  • Once the under the sink storage reservoir is depleted the flow volume will be down to a trickle until the storage reservoir fills back up with treated water, and this may take a couple of hours.
  • Some POU systems only remove Arsenic 5 (reverse osmosis).
  • POU systems usually do not have a safety tank so users will be exposed to arsenic contamination after the capacity is reached and before testing indicates the need for a replacement.
  • With a POU systen you will still be bathing, showering, brushing teeth, washing clothes and filling up swimming pools or hot tubs with arsenic-contaminated water.
  • Studies have shown that in homes with a single tap arsenic POU water treatment system, it is not uncommin for people to occasionally drink from untreated taps, and when they do, arsenic levels increase in their urine.                                                                                                                                                                                                                                                                                    
  • If POU treatment at the kitchen sink is used, the kitchen tap should be the only source of water used for drinking or cooking. If water may be used for drinking in other rooms of the home (e.g. at a bathroom sink), either a POU unit should be installed at each potential drinking water tap in the home or a Whole-House Point-of-Entry (POE) system should be used.
  • When the cost of multiple POU systems is considered, it often becomes more economical to install a Whole-House POE system.
  • Some local health departments require Whole-House POE arsenic water treatment to ensure the health of current and future homeowners
  • Test the treated water one or two weeks after the installation is complete. This is very important. Even the best water treatment professionals can make a mistake and your system may not be working due to an error. DEP staff have seen homes with the wrong media in the tank (pH adjustment media instead of arsenic treatment media). Good installations have been observed to not remove any arsenic for an entire year because of incorrect settings on the bypass valves. Hence the importance of the initial after-installation test.
  • After the initial testing shows the system is working, you should test the water at the kitchen sink and between the worker and the safety tanks (on a POE system) once every year.
  • It is much harder for arsenic treatment systems to remove arsenic when the pH of the water is greater than 8.5, and at high pH the life of the arsenic treatment media is greatly reduced.
  • In New Jersey wells with arsenic and a pH greater than 8.5, a pH adjustment tank should be included in their system.  This can be accomplished by installing an anion exchange system before the arsenic tanks. The anion exchange system will reduce the pH about one point. The anion exchange system may also remove some arsenic which will also help increase the life expectancy of the arsenic treatment media, but as we note in FAQ 16 we strongly recommend against relying on an anion exchange system to remove arsenic.
  • Well water with arsenic and pH greater than 9.5 is a more difficult situation that will require the attention and recommendation of your water treatment professional.  Injection of ascorbic acid into the water before it goes into the arsenic tanks is one example of an approach for dealing with very high pH water.
  • There are three main options for arsenic water testing:
  1. Lab Sampling - Lab Testing: The most convenient option is to schedule someone from the lab to come out and collect the samples for arsenic testing.
  2. Water Treatment Company Sampling - Lab Testing: Some water treatment professionals will provide annual testing as part of their service. Obtaining a service contract from them will take the worry away from you and protect your family's health.
  3. Homeowner Sampling - Lab Testing: You can pick up the appropriate bottles from a convenient lab, collect the water samples yourself, and deliver them to the lab.
    • A list of certified labs capable of testing arsenic by the most sensitive analytical methods can be found on our "Testing Options" page.
    • Sampling instructions:
      • Stress the system: Run two cold water taps for at least ten minutes before collecting samples. This ensures the samples will not be from stale water inthe plumbing. See FAQ#24 for more details.
      • Collect the between-the-tanks treated water sample:
        • This is the most important sample to collect when you have a two-tank Whole House system. See the picture below for the location:
      • Collect a sample of fully treated water at the kitchen sink:
        • Remember to keep two taps running for at least ten minutes while collecting the water samples to ensure the system is stressed properly and you do not test stale water from the plumbing or treatment tanks.
  • If arsenic is your only water quality problem, test for arsenic every year along with nitrates and total coliform which can change from year to year.
  • You don't need to purchase the full Private Well Testing Act (PWTA) package every year, but testing for all PWTA contaminants once every five years is recommended.
  • Yes, the treatment system needs to be stressed to be sure it works effectively when multiple taps are on at the same time.
  • To test Whole-House POE systems, you should run two cold water taps full blast for at least 10 minutes before collecting the sample between the tanks or at the klitchen sink.
  • The reason for stressing the system is that all treatment systems require contact time between the water and the treatment media to remove all the arsenic.  The more taps that are on at the same time in the home, the faster the water goes through the tanks, and this shortens the contact time.  You want to make sure the system is removing the arsenic during high water use times in the home (for example, two showers at one time, or a shower and the dishwasher or washing machine at the same time). 
  • Once per year you should test the water coming out of the kitchen tap. 
  • With a two-tank Point-of-Entry system you should also test the water between the two tanks once per year.
  • You can add a yearly recurring event to your electronic calendar to remind you that it is time to test your water.
  • You can pick a day of the year - maybe a holiday - and  always schedule your water test for that day each year. One person picked Valentine's Day for their water test reminder day saying "My love for my family reminds me to make sure they're not being exposed to arsenic."
  • No. Unfortunately the only way to tell if your arsenic treatment system is working is by a water test. Because arsenic is colorless, odorless and tasteless you would not be able to tell if it is breaking through the treatment system by looking at, tasting or smelling your water.
  • All treatment systems require pre-treatment sediment filters to be changed on a regular basis. The timing of sediment filter changes depends on the specific characteristics of your well and water. If the water pressure in the home gradually drops, the first thing to look for is a clogged sediment filter. 
  • The post-treatment sediment filters will probaby only need to be changed once a year.
  • Your treatment system installer should take care of the proper disposal of used treatment media.
  • Used arsenic tanks shoud be tightly closed and disposed of.
  • Treatment installers should never "re-bed" (empty the used media and replace with new media) in your home.
  • Used media should not be touched with bare hands.